Field characterization of suspect toxic chemicals requires the collection, isolation, and concentration of trace amounts of residues in, for example, air, soil, and liquid samples. Solid phase microextraction (SPME) is one known method developed for such a purpose using commercially-available, syringe-like SPME sample collection devices employing a variety of coated SPME fibers. The coated SPME fiber is typically housed in the needle (used for piercing a septum) of a GC-MS syringe, and can be mechanically extended and thus exposed to both collect analytes from the environment or sample fluid, and desorb analytes such as in an injection pod of a standard gas chromatograph (GC). SPME is a chemical sampling technique which adsorbs/absorbs analytes from the sample without the use of solvents or the need for exhaustive extractions. SPME presents many advantages over traditional analytical methods by combining sampling, pre-concentration, and transfer of analytes into a standard gas chromatograph (GC) for analysis.
A problem often seen in practice, however, is the use of GC injection ports to clean and condition SPME fibers. This practice poses a risk of carryover/cross contamination of non-target analytes between samplings. In addition, valuable analyst and instrumental analysis time may be wasted using a GC to clean and condition SPME fibers. Initial conditioning is typically required for new SPME fibers for time periods ranging from 0.5 to 4 hours at manufacturer-recommended temperatures ranging from 210 C. to 320 C. Additional cleaning time is also required to prepare ultra-clean SPME fibers for GC applications, such as field sampling, in order to reduce desorption time in a GC injector and ensure against carryover of contaminants or interfering chemical background.
One type of fiber conditioner addressing the aforementioned problem of GC injector usage for cleaning and conditioning, is disclosed in the article “Fiber Conditions for Solid Phase Microextraction: Design, Testing, and Application” by Koziel et al (J. High Resol. Chromatogr., 2000) As shown in FIG. 1 of the article, the fiber conditioner includes a stainless steel tube with a ceramic heating element for a heat source. The SPME fiber is inserted into an enlarged opening and positioned adjacent the heating element. Additionally, hot gas is flowed from an opposite end of the enlarged opening and directed toward the SPME fiber, and ultimately expelled through the enlarged opening. For fiber cleaning applications intended for fiber re-use, this arrangement may cause contamination of user-handled portions of a SPME device due to the expulsion of contaminants toward the SPME device, posing a potential safety risk for the analyst as well as risking cross-contamination for subsequent samplings.
There is therefore a need for an alternative SPME fiber cleaning and conditioning method and apparatus which provides safe, efficient, and effective SPME fiber cleaning and conditioning while minimizing the risk of contamination on the SPME device.